A Study on the Photometric Redshifts of Faint Blue Galaxies in CDFS

From the COMBO-17 digital sky survey data, 1,231 faint blue galaxies with photometric redshifts of 0.1 < z < 0.3 in the sky region CDFS (Chandra Deep Field South) are selected as the sample. We have studied the distributions of the photometric redshifts of these sample galaxies, in the conditions that the photometric redshifts are obtained respectively by using only optical data and by using both optical and near-infrared data. The results indicate that there are 183 galaxies whose photometric redshifts derived from both optical and infrared data are greater than 1.2, that the rms error of the derived photometric redshifts is 0.046, and that to increase the photometric SNR is also helpful for discriminating those misjudged low-redshift galaxies by using only the optical data. We have studied as well the typical spectral energy distributions (SEDs) of these galaxies in the reference system at rest. It is found that for the high-redshift galaxies the observed near-infrared flux tends to be greater than the optical flux, while for the low-redshift galaxies the observed near-infrared flux tends to be less than the optical flux.